2 Thrust Ball bearings, this is a popular size that could be used in many application that uses this size 3mm x 8mm x 3.5mm.Thrust bearings are known to high axial loads.Bearings are made of Chrome Steel.

I use these as a thrust bearing for a horizontal pendulum that is part of a semiautomatic telegraph key. They are an appropriate size for my application. One observation - the upper and lower races are not as deep as shown in the illustration.